Wing structure



Feb, 25 1936. P, E. MIERCIER 2,031,662

WING STRUCTURE Filed April 17, 1955 3 Sheets-Sheet l l VENTOR a 5% cwlz ATTO RN EY} Feb. 25, 1936. v P. E. MERCIER 2,031,662

WING STRUCTURE Filed April 17, 1935 5 Sheets-Sheet 2 Y Z I 1 VENTOR ATTORNEY fi bo 25,, 19%. P. E. MERCIER 2,031,662

WING STRUCTURE Filed April 17, 1935 3 Sheets-Sheet 3 ATTORNEY Patented Feb. 25, 1936 UNITED STATES WING STRUCTURE Pierre Ernest Mercier, Paris, France Application April 1'7,

12 Claims.

This invention relates to airplane wing construction of the type which includes a box struc ture with a stressed cover, the box structure lying within the wing and being attached to spars projecting from the fuselage of the airplane. More particularly, the invention is concerned with a wing construction which is similar to that shown in my copending application Serial No. 10,269 filed March 10, 1935, but differs therefrom in the provision of an improved means of attaching the box structure to the spars, the new attachment affording a better distribution of stresses than is obtainable with the construction disclosed in the application referred to.

In one form of the construction of my prior application, the box structure which serves as the frame work for the central portion of the wing includes a pair of longitudinal webs arranged to give the box a pentagonal form in plan. At the end of the box which is to lie adjacent the fuselage and to be connected to the spars, the webs meet to define an acute vertical dihedral angle, and at a point not far removed from the apex of this angle, each web defines an obtuse vertical dihedral angle, the webs then continuing toward the end of the wing in slightly convergent planes. Associated with the box structure are stiffening members which transmit stresses between the cover of the wing and the webs of the box, and at the top and bottom of the box, the stifiening members are arranged in two groups with the members of each group'lying substantially parallel. Each stiffening member extends from a point on one web at one side of the apex of the obtuse angle defined by that web to a point on the same web at the other side of the apex of the angle, and extending across the box between the webs are ribs, each of which preferably leads from the junction point of the end of a stiffening member of one group with one web to the junction point of the end of the corresponding stiffening member of the other group with the other web. In addition, a strong rib extends between the webs to connect the apices of the obtuse angles previously mentioned. I

' The box structure is connected to the spars by three connections, and of these connections, two lie at the apices of the obtuse angles and connect the box to the free ends of the spars, while the third connection lies at the apex of the acute angle at the extreme end of the box and connects the latter to a cross frame member, re ferred to as a bulkhead, which extends from one spar to the other. In the construction described, the webs, the cover, and the stiffening members 1935, Serial No. 16,743

for the cover are of such dimensions and arrangement that the component forces resulting from compression or tension on the cover will be balanced on the webs in every cross-sectional plane through the wing. The bending moment resulting from the forces applied to the wing is transmitted to the spars through the three points of attachment employed, and a substantial force is applied at the middle of the bulkhead connecting the spars.

According to the present invention, the box structure used is constructed in accordance with certain of the principles disclosed in my prior application, but a new type of attachment of the box structure to the spars is employed, as a result of which, there is no longer a substantial force transmitted from the apex of an acute angle at the end of the box structure to the central point of the bulkhead between the spars, but on the contrary, the stress to which the bulkhead is subjected is distributed along a substantial portion of the length of the latter. Also in the new construction, the attachment of the box structure to the spars is more rigid than that previously employed and is also simpler and easier to manufacture. The used of the new type of attachment does not, however, impair the proper distribution of stresses in the box structure and does not produce local strains which make it necessary to reinforce specificparts of the box structure. Also, the new attachment makes it possible to employ different materials in the box structure and spars, as, for example, a box structure of wood and spars of metal, the attachment accommodating differences in the rate of expansion of the two materials.

For a better understanding of the invention, reference may be made to the accompanying drawings, in which Fig. 1 is a diagrammatic view in perspective showing the general features of the box structure and its connection to the spars;

Fig. 2 is a diagrammatic plan view of the box structure showing the attachment thereof to the spars;

Fig. 3 is a view similar to Fig. 2 illustrating a modified construction;

Fig. 4 is a sectional View on the line 4--4 0 Fig. 2;

Fig. 5 is a cross-sectional view through a portion of the cover illustrating a form of stiffening member;

, Fig. 6 is a. diagrammatic view illustrating the stress distribution on the box structure;

Fig. 7 is a View similar to Fig. 6 showing the stresses applied to the extremity of one of the spars;

Fig. 8 is a diagrammatic perspective view showing details of the attachment of the box structure to the spars;

Fig. 9 is a perspective diagram showing the end construction of the spars and the bulkhead;

Fig. 10 is a perspective view of the end of the box structure showing the connecting means;

Fig..11 is a diagrammatic view in side elevation of a portion of the structure shown in Fig. 10;

Fig. 12 shows a modification of one of the connections between the box structure and spars; and

Fig. 13 is a view similar to Fig. 11, showing a modified construction.

Referring to the drawings, a portion of the box structure is shown diagrammatically in Figs. 1 and 2 lying within the wing, the outlines of which are represented by dot and dash lines. The box structure extends lengthwise of the wing and has a width equal to about one-half the length of the chord of the wing, the location of the box structure varying along the chord to some extent, as, for example, the front side of the box structure 'may be located at a point distant from the leading edge of the wing by an amount equal to'5% to 15% of the length of the chord.

As illustrated in Figs. 1 and 2, the box structure includes two webs 2B of suitable construction converging slightly in a direction toward the outer end of the wing, and cross ribs 2| connecting the webs. The box structure is enclosed within a cover 22, and between the cover and the top and bottom of the box structure are stiffening members 23, which may take the form of strips of suitable section secured to the cover, or

may be corrugations in the cover sheets. At both top and bottom of the box, the stiffening members are arranged in two groups with the members of each group lying substantially parallel and meeting the webs at oblique angles and preferably at the junctions of the webs and the ribs 2 I.

At the inner end of the box which is to be attached to spars, projecting outward from the fuselage, the webs taper in width so that the inner end of the box is wedge-shaped in longitudinal section. To produce this wedge-shaped end on the box structure, various expedients may be employed, as, for example, and as shown in Fig. 11, the lower tread 24 of each web may turn upwardly at a point spaced from its end to meet the upper tread 25 of the web, or the construction illustrated in Fig. 13 may be used, in which both treads 24, 25 converge to meet in substantially the median horizontal plane through the box structure. Lying in the plane where the wedgeshaped portion of the box begins is a rib 26 which is stronger than those used elsewhere within the box structure.

The box structure is secured to the fuselage (not shown) by means of spars 21 which are connected at a distance from their free ends by a frame member 28, referred to as a bulkhead. In the construction shown in Fig. 2, the spars converge so that they lie parallel to the webs of the box structure, while in the construction shown in Fig. 3, the spars are parallel and those portions of the webs defining the sides of the wedgeshaped end of the box structure are formed to lie parallel.

In both the constructions of Fig. 2 and Fig. 3, the end of the box member lying between the free ends of the spars is attached thereto at a.

plurality of points, one connection being to the bulkhead 28 and the others to the free ends of the spars. With such connections, the principal stresses through the connection are along vertical lines passing through the connections at the free ends of the spars and through the bulkhead 28. The shearing stresses in the webs along the lines of junction of the box and its cover set up strains in the cover which are directed obliquely to the webs asa result of the shape of the box and the direction in which the stiffening members extend. The webs, the cover strips, and the stiffening members are so dimensioned that the component forces resulting from the obliqueness of the lines of stress with respect to the webs are balanced in the Webs in every cross-sectional plane through the wing, as explained in my prior application.

The connections between the webs 20 and the free ends of the spars should not extend throughout the height of the webs for reasons made clear in Figs. 6 and 7. Under the shear load actingon thefree end portions of the spars beyond the bulkhead .28, those. portions which are generally of quadrilateral shape tend tobecome deformed, and the deformation is in a direction opposite to the deformationof the triangularportions of the webs in the wedge-shaped end of the latter. As shown inFig. 6, when the box structure is acted upon by downward vertical forces, that portion of the cover between transverse lines through the points A and B is subjected to tension .while that .part of the cover between transverse lines through the points B and C is subjected to compression. The result of these forces is to diminish the angle between the plane of the cover through the points A, B and the strong rib 26, the anglebeingindicatedby thedouble arrow D. Under the same conditions, the corresponding angle E between the free end of each spar and the upper tread thereof tends to increase as a result of shearing deformation of the web of the spar. Because of this difference in deformation, it is undesirable to connect the free end of each spar to the web of the box throughout the height of the latter, and accordingly, the connections employedat the free ends of the spars areof the pivotal type. For thispurpose, the free end of each spar is provided with a socket member 29, and a fitting 30 provided with a pin 3| is secured to the box against the, outer face of each web, the pin being received inthe socket member on a spar to establish the connection. The pivotal connection lies between the upper and lower faces of the box structure, and in the construction shown in Figs. 9, 10 and 11, each spar has a socket member near the upper surface thereof and the pin3l on each fitting 3D is near the upper tread of a web .20 of the box. In the construction shown in Fig. v13, the socket member 32 at the end of each spar lies substantially opposite the middle thereof and the fitting 33 on the box structure'has a pin 34 which lies midway between the upper and lower treads of the web 20.

The connection between the thin end of the wedge-shaped portion of the box and the bulkhead -28 is made throughout a substantial portion of the length of the bulkhead, and is made preferably by means of a plurality of brackets 35 secured to the thin end of the box and having portions 36. which overlie the top of the bulkhead and are secured thereto by suitable connecting means, such as rivets.

.Inorder to prevent deformation of the free end portions of the spars under load, a connection '31 of the cover on the spars which closes the space between the spars at the bottom thereof. This connection is preferably in the form of a sheet member 38 rolled with a channel 39 and secured to the cover 3'! and to the box structure in line with the strong rib 26. Instead of the rolled sheet member 38,- this connection may, if desired, be made by means of a hinge 40 (Fig. 12)

The attachment of the cover of the box to the spars may be made by means of angle bars 4i secured to the box structure along the upper treads of the webs 20, each angle bar having a flange which overlies the upper tread of a spar and is secured thereto by rivets.

The connections between the box structure and the spars are illustrated diagrammatically in Fig. 8 and this figure shows the pivotal connections between the sides of the box structure and the free ends of the spars and the connection along the top of the bulkhead 28 between the spars. The figure also illustrates the use of the channel member 38. In the figure, the ends of the spars are shown cut off at an angle so that the use of the channel member may be made clear. If desired, this end formation of the spars may be employed or the end surfaces of the spars may lie normal to the longitudinal axes thereof.

Details of the construction of the box structure are illustrated in Fig. 4. As there shown, each rib 2| is made of upper and lower halves 42, 43 which have overlapping end portions connected together by rivets 44. Secured to the half ribs are the cover sheets 22 with the stiffening members 23. As shown in Fig. 4, the stiffening members may be channel-shaped strips of the form shown in Fig. 5, the strips being provided with inspection openings 45 and being riveted to the cover along the sides of the channel. The webs 2B and 2! are provided with angle bars 46 along their upper and lower edges, these angle bars being riveted to channel bars 41 connected to the cover.

In some instances, it may be desired to employ a box structure and spars of different materials having different rates of expansion, and when that construction is employed, modifications are made in the connections between the box structure and the spars. In the modified construction, the connection between the thin end of the wedge portion of the box and the bulkhead 28, made by means of bracket members 35, is retained, as is also the connection by means of the channel member 38 between the cover on the spars and the box structure. The connection between the cover on the box structure and the upper treads of the spars is omitted, and the pivotal connections between the ends of the spars and the webs of the box structure are replaced by slot and'pin connections. Variation of this arrangement involves the use of pivotal connections at the ends of the spars and slot and pin connections between the thin edge of the Wedge-shaped portion of the box structure and the bulkhead.

In the construction illustrated and described, the box structure includes a pair of webs but as disclosed in my prior application, a third web 48 may be employed, this web lying in the longitudinal median plane of the box structure.

What I claim is:

1. In an airplane, the combination with a pair of spars having spaced free ends and a bulkhead connecting the spars inward from the free ends thereof, of a wing containing a box structure which includes longitudinal webs, said structure terminating at one end in a portion wedge-shaped in longitudinal section and received between the free ends of the spars, a connection between each side of the box structure and the adjacent spar near the free end thereof, and a connection between the thin end of the wedge and the bulkhead, said connection extending throughout a substantial portion of the length of the bulkhead.

2. In an airplane, the combination with a pair of spars having spaced free ends and a bulkhead connecting the spars inward from the free ends thereof, of a wing containing a box structure which includes longitudinal webs, said structure terminating at one end in a portion wedge-shaped in longitudinal section and received between the free ends of the spars, a pivotal connection between each side of the box structure and the adjacent spar near the free end thereof, and a connection between the thin end of the wedge and the bulkhead, said connection extending throughout a substantial portion of the length of the bulkhead.

3. In an airplane, the combination with a pair of spars having spaced free ends and a bulkhead connecting the spars inward from the free ends thereof, of a wing containing a box structure which includes longitudinal webs, said structure terminating at one end in a portion wedge-shaped in longitudinal section and received between the free ends of the spars, a connection between each side of the box structure and the adjacent spar near the free end thereof, and connections between the thin end of the wedge and the bulkhead at a plurality of points distributed along the length of the bulkhead.

4. In an airplane, the combination with a pair of spars having spaced free ends, a bulkhead connecting the spars inward from the free ends thereof, and a cover closing the space between the spars on at least one side of the spars, of a wing containing a box structure which includes longitudinal webs, said structure terminating at one end in a portion wedge-shaped in longitudinal section and received between the free ends of the spars, a connection between each side of the box structure and the adjacent spar rear the free end thereof, a connection between the thin end of the wedge and the bulkhead throughout a substantial portion of the length of the latter, and a connection between the cover on the spars and the box structure adjacent the base of the wedgeshaped portion thereof.

5. In an airplane, the combination with a pair of spars having spaced free ends, a bulkhead connecting the spars inward from the free ends thereof, and a cover closing the space between the spars on at least one side of the spars, of a wing containing a box structure which includes longitudinal webs, said structure terminating at one end in a portion wedge-shaped in longitudinal section and received between the free ends of the spars, a connection between each side of the box structure and the adjacent spar near the free end thereof, a connection between the thin end of the wedge and the bulkhead throughout a substantial portion of the length of the latter, and a yielding connection between the cover on the spars and the box structure adjacent the base of the wedge-shaped portion thereof.

6. In an airplane, the combination with a pair of spars having spaced free ends, a bulkhead connecting the spars inward from the free ends thereof, and a cover closing the space between the spars on at least one side of the spars, of a wing containing a box structure which includes longitudinal webs, said structure terminating at one end in a portion wedge-shaped in longitudinal section and received between the free ends of the spars, a rib connecting the webs at the baseof the wedge-shaped portion, a connection between .each web opposite said rib and the adjacent spar near the free end of the latter, and a connection between the thin end of the wedge-shaped-portion and the bulkhead throughout a substantial portion of the length of the latter.

'7. In an airplane, the combination with a. pair of spars having spaced free ends, a bulkhead connecting the spars inward from the free ends thereof, and a cover closing the space between the spars on at least one side of the spars, of a wing containing a box structure which includes longitudinal webs, said structure terminating at one end in a portion wedge-shaped in longitudinal section and received between the free ends of the spars, a rib connecting the webs at the base of the wedge-shaped portion, a connection between each web opposite said rib and the adjacent spar near the free end of the latter, a connection between the thin end of said wedge-shaped portion and said bulkhead throughout a substantial portion of the length of the latter, and a connection between the cover on the spars and the box structure along one face of said rib.

8. In an airplane, the combination with a pair of spars having spaced free ends, a bulkhead connecting the spars inward from the free ends thereof, and a cover closing the space between the spars on at least one side of the spars, of a wing containing a box structure which includes longitudinal webs, said structure terminating at one end in a portion wedge-shaped in longitudinal section and received between the free ends of the spars, a connection between each side of the box structure and the adjacent spar near the free end thereof, and a connection between the thin end of the wedge-shaped portion and one side face of the bulkhead throughout a substantial portion of the length of the bulkhead.

9. In an airplane, the combination with a pair of spars having spaced free ends, a bulkhead connecting the spars inward from the free ends thereof, and a cover closing the space between the spars on at least one side thereof, of a wing comprising a box structure made up of longitudinal webs and cross ribs, and a cover on said box structure stiflfened along lines lying oblique to the faces of the webs, the box structure terminating at one end in a portion wedge-shaped in longitudinal section and received between the free ends of the spars, a connection between each side of the box structure at the base of the wedge-shaped portion and the adjacent spar near the free end thereof, and a connection between the thin end of the wedge-shaped portion and the bulkhead throughout a substantial portion of the length of the latter.

10. In an airplane, the combination with a pair of spars having spaced free ends, a bulkhead connecting the spars inward from the free ends thereof, and a, cover closing the space between the spars on at least one side thereof, of a wing comprisinga'box structure made up of longitudinal websandcross ribs, and a cover on said box .gstructure stiffened along lineslying oblique to the facesof the-webs, the box structure terminating at one end in a portion wedge-shaped in longiitudinalsection and received between the free ends of the spars, a connection between each side of the box structure at the base of the wedgeshaped portion and the adjacent spar near the free end thereof, a connection between the thin end of the wedge-shaped portion and the bulkhead throughout .a substantial portion of the length of the latter, and a connection between the spars on at least one side thereof, of a wing comprising a, box structure made up of longitudi nal webs and cross ribs, and a cover on said box structure stiffened along lines lying oblique to the faces of the webs, the box structure terminating at one end in a portion wedge-shaped in longitudinal section and received between the free ends of the spars, a connection between each side of the box structure at the base of the wedgeshaped portion and the adjacent spar near the free end thereof, one end of the box structure being received between the free ends of the spars, a connection between each side of the box structure and the adjacent spar near the free end thereof, a connection between the end of the box structure and the bulkhead throughout a substantial portion of the length of the latter, a connection between the spar cover and the box structure cover adjacent the free ends of the spars and extending from one spar to the other, and connections between the treads of the spars and the box cover.

12. In an airplane, the combination with a pair of spars having spaced free ends, a bulkhead connecting the spars inward from the free ends thereof, and a cover closing the space between the spars on at least one side thereof, of a wing comprising a box structure made up of longitudinal webs and cross ribs, and a cover on said box structure stiffened along lines lying oblique to the faces of the webs, the box structure terminating at one end in a portion wedge-shaped in longitudinal section and received between the free ends of the spars, a connection between each side of the box structure at the base of the wedgeshaped portion and the adjacent spar near the free end thereof, a connection between the thin end of the wedge-shaped portion and the bulkhead throughout a substantial portion of the length of the latter, a connection between the spar cover and the box structure adjacent the base of the wedge-shaped portion, and connections between the treads of the spars and the treads of the adjacent webs throughout a substantial portion of the length of the wedge-shaped portion.

PIERRE ERNEST MERCIER. 

